<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        var obj = {name:'Tom',age:'16'};
        for(var k in obj){
            document.write(k+'-'+obj[k]);
        }
    </script>
    <script>
     var obj = {name:'Tom',age:'16'};
     console.log('name'in obj);
     console.log('gender'in obj);
    </script>
</body>
</html>